Stabilization of light distillate produced in distilling or cracking hydrocarbons



Feb. 6, 1934. R c COOK STABILIZATION OF LIGHT DISTILLATE PRODUCED IN DISTILLING OR CRACKING HYDROCARBONS Filed March 27, 1929 Patented Feb. 6, 1934 UNITED STATES PATENT OFFICE STABILIZATION OF LIGHT DISTILLATE PRODUCED IN DISTILLING OR CRACKING HYDROCARBONS Application March 27.

2 Claims.

This invention relates to a process for stabilizing unfinished light distillates. more particularly those distillates produced by cracking processes.

The commercial cracking processes produce unfinished distillates. highly volatile in nature. which. in finishing. are likely to suffer relatively large losses due to evaporation of the lighter constituents.

The salient object of the present invention is to remedy this condition. and provide a method whereby these losses will be minimized.

The method of this invention requires: removing the distillate directly after the separation of the fixed gas therefrom: heating the disti late to a moderate degree to drive off any dissolved gas and vaporize the lighter condensable hydrocarbons; passing the gas and vaporized lighter constituents preferably through a chemical treating means: and. finally absorbing the gas and vaporized lighter constituents in a heavier gasoline or naphtha or the heavier ends of the gasoline resulting from the cracking process after chemical treatment and redistillation.

The single figure represents a diagrammatic elevational view of apparatus by which the process can be carried out.

Referring in detail to the drawing. raw oil is supplied through line 1 where by regulation of valves 2 and 3, it may either enter the dephlegmator or pass directly to the tube bank or be split.

In the preferred operation. valve 3 will be closed and valve 2 opened; thus the raw oil is fed through line 4 to the top of dephlegmator 5. The reflux condensate. together with the preheated raw oil will then pass down through dephlegmator leg 6, and hot oil pump 7. to the inlet of coil 8. located in furnace 9. The heated oil will pass out through transfer line 10. controlled by valve 11 to reaction chamber 12. where vapors separate from non-vaporous products of reaction. The latter may be withdrawn through valve 13 to storage. or for other purposes. Vapors from reaction chamber 12 pass out through line 14. controlled by valve 15 into dephlegmator 5. Vapors from dephlegmator 5 will pass out through line 16. controlled by valve 17 into condenser coil 18. from which the condensate and non-condensable gas will pass into receiver 19.

Pressure at this point may be controlled by release of non-condensable gas through valve 20. A portion of the distillate may be recirculated from receiver 19 through pump 21. valve 22 and line 23. back to the top of the dephlegmator 5.

1929. Serial No. 350,414

The rest of the condensate will be withdrawn through valve 24. in line 25. and passed to a vaporizer or stabilizer 26 where it is heated to a moderate temperature; say. from 110 F. to 150 Ft. depending upon the pressure at this point.

A source of heat for the stabilizer 26 may be from the partially condensed pressure distillate vapors from condenser coil 18. which may be introduced from any point a through proper valves b into a closed coil in the bottom of the stabilizer, the condensate being allowed to flow out back to the condenser coil at point 0. By regulation of valves 12 and d any desired temperature may be maintained in the stabilizer 26.

Other means of heating may be employed, for instance. live or exhaust steam may be introduced through line 27 and valve 28 (valves b and d being closed), the condensed water being allowed to drain ofl through valve 29.

A level in the stabilizer should be maintained at a given point 30. which may be observed through sight glass 31. In flowing down to the outlet 31'. the pressure distillate will be stabilized by vaporization of the dissolved gas and lighter condensable fractions. and will pass out through valve 32 to a cooling coil 33. and to storage for chemical treatment.

The vapors from stabilizer 26 will pass out through line 34. cooler coil 35. and through line 36, to a wash tower 3'7, where a doctor or caustic soda wash may be introduced. as shown, through line 38. The partially spent reagent may be withdrawn through line 39 and recirculated or withdrawn altogether. and new reagent supplied through line 38 as required.

The treated vapors and uncondensed gas will pass out through line 40 into the bottom of absorber 41. which may be of packed. baifled. or bubble type construction. In passing up through absorber 41. the vapors and uncondensed gas will pass counter-currently to an absorbing medium. preferably naphtha or heavy gasoline of proper end point introduced through line 42, which will absorb the condensable materials. allowing the stripped gas to pass out through line 43 for fuel or other purposes. The enriched absorbing medium will pass out through line 44 to finished gasoline storage.

Pressure on vaporizer 26 should preferably be only that necessary to maintain fiow through the system from that point to the outlet on the top of the absorber 41.

An example of operating conditions on a run in which this apparatus was used follows: An Oklahoma gas oil of 36 gravity was introduced into the dephlegmator 5, passed together with the reflux condensate therefrom through pump 7 to the inlet of coil 8, at a pressure of approximately 300 pounds, and at a temperature of approximately 780 degrees F. Temperature at the outlet of coil 8 was approximately 900 degrees F., and the pressure inside the reaction chamber 12 was approximately 225 pounds and that on the receiving drum 19 was approximately 200 pounds.

About 20% of residuum was withdrawn through valve 13, having a gravity of approximately 16 B. About 75% of distillate was recovered in receiver 19, having a gravity of around 55 Be'., an initial 01 approximately 90 degrees F., and end point of about 525 degrees F. This distillate was passed to stabilizer 26 on which was required a pressure of approximately 10 pounds.

The heated and stabilized distillate was drawn on through valve 32. at a temperature of about 130 degrees F., and was cooled in coil 33 to approximately 90 degrees F. A 52 degree Baum gravity treated naphtha was introduced into the absorber 41, through line 42. Gravity on this naphtha was raised to about 58 degrees Baum and represented in distillation characteristics a balanced U. S. motor gasoline.

A very small amount of fixed gas was withdrawn through line 43 and was used for fuel in the process. A very slight pressure was maintained on absorber 41 through the agency of valve 45 in order to convey the non-condensable gas therefrom to the burners.

I claim as my invention:

1. A process for treating the gasoline-like vaporous product produced in the cracking of hydrocarbon oils which comprises subjecting the same to condensation in a condensing zone and separating the resultant distillate from the fixed gases, withdrawing a portion of the vaporous products from said zone, moderately heating said distillate by passing in heat exchange relation therewith the portion of the vaporous product withdrawn from the condensing zone. said heating being of such character as to remove from the distillate dissolved gases and vapors lighter than gasoline, returning said portion of the vaporous products to the condensing zone, and collecting the unvaporizd stabilized distillate independently of the evolved vapors and gases. I

2. A process for treating the gasoline-like vaporous product produced in the cracking of hydrocarbon oils which comprises subjecting the same to condensation in a condensing zone and separating the resultant distillate from the fixed gases, withdrawing a. portion of the vaporous products from said zone, moderately heating said distillate by passing in heat exchange relation therewith the portion of the vaporous product withdrawn from the condensing zone, said hea ing being of such character as to remove from the distillate dissolved gases and vapors lighter than gasoline, returning said portion of the vaporous products to the condensing zone collecting the unvaporized stabilized distillate independently of the evolved vapors and gases, and scrubbing RALPH C. COOK. 

